LwIP怎么拥有PING其他设备的能力？

太久没回来看帖，帐号直接被冻结。
其实机制很简单，ICMP其实基于IP层的，发送的时候只需要根据ICMP包的协议自己组一个一样的协议包就可以。至于时间的计算就是在发送的时候先获取一下单片机的运行时间，然后在ICMP Respond解析那里再一次获取一下单片机的运行时间，两个时间一减就是PING包的时间，不过肯定是有点延时的，但现在用起来其实还可以。
上码，不BB。
ICMP发送：
err_t
udp_sendicmp(struct udp_pcb *pcb, struct pbuf *p,
  struct ip_addr *dst_ip, u16_t dst_port)
{
  struct netif *netif;
  LWIP_DEBUGF(UDP_DEBUG | LWIP_DBG_TRACE | 3, ("udp_sendn"));
  /* find the outgoing network interface for this packet */
#if LWIP_IGMP
  netif = ip_route((ip_addr_ismulticast(dst_ip))?(&(pcb->multicast_ip))dst_ip));
#else
  netif = ip_route(dst_ip);
#endif /* LWIP_IGMP */
  /* no outgoing network interface could be found? */
  if (netif == NULL) {
    LWIP_DEBUGF(UDP_DEBUG | 1, ("udp_send: No route to 0x%"X32_F"n", dst_ip->addr));
    UDP_STATS_INC(udp.rterr);
    return ERR_RTE;
  }
  return udp_sendto_ping(pcb, p, dst_ip, dst_port, netif);
}
err_t
udp_sendto_ping(struct udp_pcb *pcb, struct pbuf *p,
  struct ip_addr *dst_ip, u16_t dst_port, struct netif *netif)
{
        //  struct udp_hdr *udphdr;
        struct ip_addr *src_ip;
        err_t err;
        struct pbuf *q; /* q will be sent down the stack */
        struct icmp_echo_hdr *icmphdr; //kaishui
        /* not enough space to add an UDP header to first pbuf in given p chain? */
        if (pbuf_header(p, sizeof(struct icmp_echo_hdr))) {
                /* allocate header in a separate new pbuf */
                //        q = pbuf_alloc(PBUF_IP, sizeof(struct icmp_echo_hdr), PBUF_RAM);
                q = pbuf_alloc(PBUF_IP, sizeof(struct icmp_echo_hdr)+ IP_HLEN + ICMP_DEST_UNREACH_DATASIZE,
                        PBUF_RAM);
                /* new header pbuf could not be allocated? */
                /* chain header q in front of given pbuf p */
                pbuf_chain(q, p);
                /* first pbuf q points to header pbuf */
        }
  
        /* q now represents the packet to be sent */
        icmphdr = (struct icmp_echo_hdr *)q->payload;
        icmphdr->type = 8;
        icmphdr->code = 0;
        icmphdr->id =htons(0x0100)  ;     
        icmphdr->seqno =htons(0x51d1);
        icmphdr->chksum = 0;  
        //   icmphdr->chksum = inet_chksum(p->payload, 10);
        icmphdr->chksum = inet_chksum(icmphdr, q->len);
        /* PCB local address is IP_ANY_ADDR? */
    if (ip_addr_isany(&pcb->local_ip))
        {
                /* use outgoing network interface IP address as source address */
                src_ip = &(netif->ip_addr);
    }
        else
        {
                /* check if UDP PCB local IP address is correct
                 * this could be an old address if netif->ip_addr has changed */
                /* use UDP PCB local IP address as source address */
                src_ip = &(pcb->local_ip);
        }
        err = ip_output_if(q, src_ip, dst_ip, pcb->ttl, pcb->tos, IP_PROTO_ICMP, netif);
        snmp_inc_udpoutdatagrams();
        /* did we chain a separate header pbuf earlier? */
        if (q != p)
        {
                /* free the header pbuf */
                pbuf_free(q);
                q = NULL;
                /* p is still referenced by the caller, and will live on */
        }
        UDP_STATS_INC(udp.xmit);
        pbuf_free(p);//important
        return err;
}
void PingInit(void)
{
        struct ip_addr ipaddr;
        unsigned int port = 2000; //69
        p = pbuf_alloc(PBUF_RAW,10,PBUF_RAM);
        p->payload=(void *)UDPData;
        IP4_ADDR(&ipaddr,0,0,0,0);  
        UDPpcb = udp_new();
        udp_bind(UDPpcb,&ipaddr, port);
}
void ICMP_Ping(void)
{
        struct ip_addr dstipaddr;
               
        p = pbuf_alloc(PBUF_RAW,10,PBUF_RAM);
        p->payload=(void *)UDPData;
               
        OSTimeDlyHMSM(0, 0, 0, 500);        //wait 200ms
        memcpy(&dstipaddr.addr,&flash_read.lwip_msg->dns2,4);               
       
        if(mt_client.respond_flag ==0)
        {
                cnt_1ms = 0;
        }
        else
        {
                mt_client.ping_end.end_time.tv_usec = 1000;
                mt_client.timeout_flag = 1;
        }
        udp_sendicmp(UDPpcb,p,&dstipaddr,2000);
        mt_client.respond_flag = 1;
        ntx_packet++;
        mt_client.ping_before.end_time.tv_sec = get_running_time();
        mt_client.ping_before.end_time.tv_usec = get_1mstime();//ms         
}
ICMP接收：（icmp.c）
void
icmp_input(struct pbuf *p, struct netif *inp)
{
   ....
     case ICMP_ER:
    /* This is OK, echo reply might have been parsed by a raw PCB
       (as obviously, an echo request has been sent, too). */
#ifdef PINGPACK_TEST               
        nrx_packet ++;
        mt_client.ping_after.end_time.tv_sec = get_running_time();
        mt_client.ping_after.end_time.tv_usec = get_1mstime();//ms
        mt_client.ping_end.end_time.tv_sec = 0;
        mt_client.ping_end.end_time.tv_usec = mt_client.ping_after.end_time.tv_usec - mt_client.ping_before.end_time.tv_usec;
        mt_client.respond_flag = 0;
        if(mt_client.ping_end.end_time.tv_usec > 10)//ms
        {
                mt_client.timeout_flag = 1;
        }
#endif  
    break;
    ...
｝

@原子哥速来求解，感谢！！！

这个功能没用过哦,帮顶.

已经通过UDP的方式发送ping包了，但是要取得respond的延时时间，还在搞